Electricity + Control May 2015

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STANDBY + BACK-UP
the number of production lines, the entire process outage can range
between one to four hours. In many cases the extruder itself will be
restarted immediately after the sag, however if the extruder is not
restarted immediately and the molten material is allowed to remain
in the extruder, it can burn when reheated and as a result, the burned
particles will emerge from the extruder gradually, over a period of
several days, resulting in a poor quality product.
As such, the cost of such a burn would be much higher as opposed to
just discarding the excess polypropylene after extrusion. Furthermore,
the workforce cleans the equipment and therefore there is neither an
increase nor a decrease in labour costs. Another major influencing
factor concerning the financial loss is whether or not the factory pro-
duction runs continuously. In continuous production, the production
lost during downtime cannot be recovered by working extra time, so
loss of production translates directly into loss of profit – that is, the
loss is equal to the value of the product not produced as a result of
the downtime. The cost associated with line trips owing to an outage
can run into tens and hundreds of thousands of Rands per outage.
Cost incurred may be owing to:
• Downtime
• Scrap product
• Cleaning of the system before being able to restart
Plant restarts as a result of dips increases maintenance and opera-
tional costs and drastically decreases equipment life span.
Solutions available on the market
Uninterrupted online power supplies
This solution offers continuous load power that is generated from a
storage battery. The battery is constantly charged from the power
supply, and provides immunity to dips. Installing an Uninterruptible
Power Supply (UPS) will minimise the interruption process. The down
side to this approach lies in the battery itself. The disadvantages in
using lead acid batteries are:
• They generate hydrogen gas and must, therefore, be ventilated
• Battery lead is a hazardous waste product
• The battery life is limited and decreases rapidly when cycled often
It should also be mentioned that UPSs generated amounts of current
harmonics onto the system and end-users should install additional
harmonics filter in order to minimise the level of harmonics. For
example, a high capacity UPS will require additional accessories in
order to meet the needs and requirements of the utility. Not to forget
the fact that apart from all these considerations − the price is high
for large loads.
Providing voltage stability
The Equalizer Turbo has been specifically designed to meet the
needs for a wide range of manufacturers − as well as for the plastic
extrusion or papermaking industries. It provides a ride-through three
phase 0,4 pu, voltage dip ∆ U 60 %with a typical duration set for three
seconds. Clients may specify an even longer duration to meet their
individual requirements for production. This ride-through capabil-
ity easily resolves almost all the voltage disruptions in developed
countries.
Additional advantages include:
• Restoring the voltage to 1,0 pu of its nominal value (+-15 %)
• Correcting each phase accurately and independently owing to
independent phase compensation, the Equalizer Turbo can
• Having an integrated software monitoring system with event
notification and remote access
Conclusion
The Turbo will not generate or inject any current harmonics into the
system owing to its electronic switching technology at current zero
crossing. In addition, it will not cause any harmonic-related problems
(i.e. no additional requirement of costly filters). In contrast, the UPS
generates a high amount of current harmonics to the system, requir-
ing harmonic filters. High capacity UPSs require additional accessories
to match utility requirements.
Reference
[1] IEEE 1159. 2009. Recommended practice for monitoring power
quality.
Abbreviations/Acronyms
PLC – Programmable Logic Controller
rms – root mean square
UPS – Uninterruptible Power Supply
take note
This ride-through capability easily
resolves almost all the voltage disruptions
in developed countries.
Sishal Kuwar-Kanaye has spent several years in HV project, commissioning
and maintenance environments. He holds a BTech Elec degree, a Masters
Certificate in Project Management (GWCPM), Certified Energy Manager
(CEM), Certified Measurements and Verification Professional (CMVP) and
he is registered with ECSA. He is Group Project Engineer at Impact Energy.
Enquiries: Email
• Sags are short-term reductions in the rms magnitude of
the supply voltage lasting from a fraction of a second up to
several seconds.
• Many dips are caused by faults on the supply network.
• The Equalizer Turbo has been designed to provides a ride-
through three phase voltage dip with a typical duration set
for three seconds.
33 May ‘15 Electricity+Control